Commonway
Version V. 2026.09.03

Displaced Left-Turn (DLT) retrofit

RFT-INT-04 Intersection

Displaced Left-Turn (DLT) retrofit

Shifts the left-turn lane to the opposing side of oncoming traffic upstream of the main intersection, letting left-turning and opposing through traffic move simultaneously without a dedicated protected phase.

#Overview

Also known as a continuous flow intersection, this retrofit resolves the same unprotected-left-turn conflict that Median U-Turn and RCUT address, but through signalized displacement rather than a median crossover. A driver turning left crosses opposing traffic at a signal well before the main intersection, then proceeds through the main intersection on a green phase running concurrently with through traffic in both directions, since the crossing conflict has already been resolved upstream.

#Where this leads: Target patterns

Displaced Left-Turn (DLT) (INT-DLT-14)

#Applicability and thresholds

Requires substantial additional right-of-way width upstream of the main intersection to build the displaced left-turn crossing, which is this retrofit's primary limitation compared to Median U-Turn or RCUT.2 Most viable at high-volume urban or suburban intersections where a grade-separated interchange isn't justified but conventional signal delay from protected left-turn phasing is severe.

#Evidence and effectiveness

DLT is documented as a faster, lower-cost alternative to a grade-separated interchange at high-volume intersections, resolving left-turn and through-movement conflicts without the cost of a flyover or underpass, though at higher construction cost and impact than Median U-Turn or RCUT.1

#Getting it built

Cannot be piloted informally. Widening for the displaced left-turn crossing is real, costly construction, frequently impacting adjoining properties given the additional area required. This strategy effectively starts at Permanent on the construction spectrum. See Construction Methodology & The Build Spectrum.

An Intersection Control Evaluation is standard practice, and given the higher cost and impact of this design relative to Median U-Turn or RCUT, is particularly important for justifying the additional expense. See Decision & Evaluation Processes.

#Who can move this

Typically a state DOT or large-city capital project, given the cost and right-of-way scope involved. See Legal & Planning Mechanisms and Funding & Financing Mechanisms.

Median U-Turn (MUT) retrofit (RFT-INT-02), Restricted Crossing U-Turn (RCUT) retrofit (RFT-INT-03) (the two lower-cost alternatives addressing the same underlying unprotected-left-turn problem)

#References

  1. Evidence-based "Unconventional Arterial Intersection Designs under Connected and Automated Vehicle Environment: A Survey," on Displaced Left-turn Intersection design and cost tradeoffs relative to grade-separated interchanges.
  2. Legal / regulatory U.S. Patent 7,135,989, "Parallel flow vehicle turn system for traffic intersections," on displaced left-turn retrofit considerations and right-of-way impacts.

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